Capacitive sensors may include one or more capacitors, the value of which indicates a sensed parameter. A detection circuit may measure values of capacitors included in a capacitive sensor to determine values of the sensed parameters indicated by the capacitive sensor. For example, a capacitive accelerometer may produce one or more capacitance values based on an acceleration experienced by the accelerometer. A detection circuit connected to the capacitive accelerometer may measure the one or more capacitance values and determine acceleration of the accelerometer based on the values.
In some implementations, accelerometers may include a sensing element that includes two parallel plate capacitors acting in a differential manner in which acceleration of the accelerometer causes one of the capacitors to increase in capacitance and the other capacitor to decrease in capacitance. At rest, or at a constant acceleration, the difference between capacitances in the accelerometer may remain constant. A detection circuit may determine the values of the capacitances in the accelerometer by applying a voltage to the capacitors, e.g., a square wave voltage, and producing an output voltage associated with the capacitors. The output voltage produced may be digitized using an analog to digital (A/D) converter in order to produce a digital value that indicates the amount and direction of acceleration that is suitable for use in digital systems. Typically, the detection circuit used for determining the digital values of the two capacitances may include amplifiers, filters, oscillators, A/D converters etc.